Technical Field
The present disclosure relates generally to sensors for biomolecule sensing, and more particularly to structures and methods for making measurements from a liquid solution including biomolecules.
Description of the Related Art
Bio-molecule sensing is important in healthcare. One example of bio-molecule sensing is referred to as surface plasmon resonance spectroscopy, generally designated as SPR (surface plasmon resonance). This method is based upon the optical excitation of surface plasmons in thin metal layers. The resonance conditions for the excitation of surface plasmons strongly depend on the optical properties of the dielectrics surrounding the metal layer. Hence, it is principally feasible to determine the refractive index and the layer thickness of thin dielectric layers with high precision. SPR-spectroscopy finds an increasing application in biochemical analysis, since it permits a direct analysis of the interactions between the bio-molecules (for example, antibody/antigen reactions at or near the sensor surface). To this end a reactant (ligand) is immobilized on the metal surface, and the other reactant (analyte) in solution is passed over the surface. The interaction can be directly detected as a change in dielectric constant (refractive index) which can be translated into an increase in layer thickness. There is no marking of the reactants necessary as, for example, with the radioimmunoassay (RIA) or the enzyme-linked immunosorbent assay (ELISA). A drawback that is common to SPR is false positives.